derivco-pointerevents
v1.0.0
Published
Polyfill of the PointerEvents W3C spec
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Pointer Events Polyfill - making pointer events usable today
PEP polyfills pointer events in all browsers that haven't yet implemented them, providing a unified, responsive input model for all devices and input types. You can read more about pointer events below.
Getting Started
- Place the PEP script in the document head
<script src="https://code.jquery.com/pep/0.4.1/pep.js"></script>
By default, no pointer events are sent from an element. This maximizes the possibility that a browser can deliver smooth scrolling and jank-free gestures. If you want to receive events, you must set the
touch-action
property of that element. Set up some elements to create events with thetouch-action
attribute.Listen for the desired events
pointermove
: a pointer moves, similar to touchmove or mousemove.pointerdown
: a pointer is activated, or a device button held.pointerup
: a pointer is deactivated, or a device button released.pointerover
: a pointer has moved onto an element.pointerout
: a pointer is no longer on an element it once was.pointerenter
: a pointer enters the bounding box of an element.pointerleave
: a pointer leaves the bounding box of an element.pointercancel
: a pointer will no longer generate events.
- As elements come and go, or have their
touch-action
attribute changed, they will send the proper set of pointer events.
<html lang="en">
<head>
<meta charset="utf-8">
<title>PEP (Pointer Events Polyfill)</title>
<meta name="viewport" content="width=device-width">
<!-- include PEP -->
<script src="https://code.jquery.com/pep/0.4.1/pep.js"></script>
</head>
<body>
<button id="b" touch-action="none">Test button!</button>
<p><output id="o"></output></p>
<script>
document.getElementById( "b" ).addEventListener( "pointerdown", function( e ) {
document.getElementById( "o" ).innerHTML = "that was a " +
e.pointerType + " " + e.type + " on a "+ e.target.nodeName;
} );
</script>
</body>
</html>
See also the examples in the W3C Pointer Events Specification and our own samples for using PEP.
Using PEP with jQuery
You can use pointer events with jQuery and PEP:
<div id="canvas" touch-action="none"></div>
<script src="pep.dist.js"></script>
<script src="jquery.js"></script>
<script>
$("#canvas").on("pointermove", function(event) {
draw(event);
});
</script>
Check out this jsbin demo for a full demo.
jQuery doesn't copy all properties from the original event object to the event object provided in the event handler. You can find a list of copied and normalized properties on the jQuery API docs. To access any other original properties, use event.originalEvent
.
Why Pointer Events?
Mouse events and touch events are fundamentally different beasts in browsers today, and that makes it hard to write cross-platform apps.
For example, a simple finger paint app needs plenty of work to behave correctly with mouse and touch:
Current platforms that implement touch events also provide mouse events for backward compatibility; however, only a subset of mouse events are fired and the semantics are changed.
- Mouse events are only fired after the touch sequence ends.
- Mouse events are not fired on elements without a
click
event handler. One must be attached by default, or directly on the element withonclick
. click
events are not fired if the content of the page changes in amousemove
ormouseover
event.click
events are fired 300ms after the touch sequence ends.- More information: Apple Developer Documentation.
Additionally, touch events are sent only to the element that received the touchstart
. This is fundamentally different than mouse events, which fire on the element that is under the mouse. To make them behave similarly, touch events need to be retargeted with document.elementFromPoint
.
These incompatibilities lead to applications having to listen to 2 sets of events, mouse on desktop and touch for mobile.
This forked interaction experience is cumbersome and hard to maintain.
Instead, there should exist a set of events that are normalized such that they behave exactly the same, no matter the source: touch, mouse, stylus, skull implant, etc. To do this right, this normalized event system needs to be available for all the web platform to use.
Thus, Pointer Events!
Polyfill Limitations
touch-action
According to the spec, the touch-action CSS property controls whether an element will perform a "default action" such as scrolling, or receive a continuous stream of pointer events.
Due to the difficult nature of polyfilling new CSS properties, this library will use a touch-action attribute instead. In addition, run time changes involving the touch-action
attribute will be monitored for maximum flexibility.
Touches will not generate events unless inside of an area that has a valid touch-action
attribute defined. This is to maintain composition scrolling optimizations where possible.
Browser Compatibility
PEP should work on IE 10+ and the latest versions of Chrome, Safari, Firefox, and Opera. In any browser implementing pointer events natively (detected by checking for window.PointerEvent
), PEP won't do anything.